As a portable transmitter or receiver, a watch with an FM radio and a watch-shaped individual-selective-calling receiver have been known. In such a watch-type apparatus, an electrically conductive plate member or film is put in a watchband for mounting an apparatus body at a wrist. Therefore, when the watchband is mounted at the wrist, a loop antenna is formed by the plate member or film.
In such a communication apparatus, as typically shown in FIG. 9(b), the apparatus body includes a circuit board 73 on which a high-frequency analog IC 93B for transmission or receiving and a signal-processing digital IC 94B which is driven by a driving signal having a frequency as high as several MHz are mounted. These ICs (collectively indicated by A.cndot.B-IC in the figure) are wire-bonded on the rear surface section 732 of the circuit board 73 at the rear surface side (side where the entire or most part of a loop antenna 4 is disposed) of the circuit board 73. At the front surface side (side where a liquid crystal display panel 6 is disposed) of the circuit board 73, a display digital IC 95B (indicated by C-IC in the figure) which is driven by a several-tens-of-kHz driving signal is mounted on the front surface section 721 of a circuit board 72 by wire bonding.
Through various examinations into the effect of high-frequency noise in a wrist-mount-type communication apparatus, the inventor of this application found that sensitivity is low when the high-frequency analog IC 93B or the signal-processing digital IC 94B is wire-bonded to the rear surface section 732 of the circuit board 73. In other words, irrespective of high-frequency noise generated from the active surface (meaning a surface on which leads are exposed, a wiring surface, and a device surface) 930B or 940B of the high-frequency analog IC 93B or the signal-processing digital IC 94B, when the high-frequency analog IC 93B or the signal-processing digital IC 94B is disposed conventionally such that the active surface 930B or 940B faces the loop antenna 4, it is because the loop antenna 4 is susceptible to the effect of the high-frequency noise.
In consideration of the foregoing problem, it is an object of the present invention to provide a highly sensitive communication apparatus which reduces the effect of high-frequency noise generated from the active surface of an IC by appropriately disposing the IC that serves as a noise source.